70 PRACTICAL ANATOMY. 



lacerated, which is under the cover of the lesser wings of 

 the sphenoid ; the foramen rotundum, the foramen ovale, 

 the middle lacerated, the foramen spinosum, the hiatus 

 Fallopii, and the opening of the carotid canal. The pos- 

 terior fossa is bounded in front by the posterior surface of 

 the petrous portion and the incline of the basilar process 

 of the occipital bone; laterally by the occipital, parietal, 

 and mastoid portion of the temporal. It is strongly con- 

 cave in every direction, and lodges the cerebellum, the 

 medulla, and the posterior lobes of the brain. The 

 principal foramina are the posterior lacerated, anterior 

 condyloid, and the foramen magnum. The posterior 

 condyloid and the mastoid, when present, transmit veins. 

 The interior of the cranial cavity presents certain grooves, 

 some of which are constant and invariable in position. 

 These grooves lodge the blood-sinuses which are formed 

 by the divergence of the layers of the dura mater. The 

 principal grooves are the following: The groove for the 

 superior longitudinal sinus; it begins at the foramen 

 caecum, and, gradually growing broader, curves back- 

 ward along the median line, terminating at the internal 

 occipital protuberance. A slight groove is continued 

 downward toward the foramen magnum for the accom- 

 modation of an ascending sinus. The grooves for the 

 lateral sinuses are very large and important. They pass 

 horizontally outward from the internal occipital protuber- 

 ance, on the horizontal limb of the occipital cross, as far 

 forward as the mastoid portion of the temporal, then 

 curve downward behind the petrous portion, then inward, 

 and terminate at the posterior lacerated foramina, through 

 which the lateral sinuses pass, assuming the name of 

 jugular vein. The superior and inferior petrosal sinuses 

 groove the superior and posterior borders of the petrous 

 part of the temporal, and communicate with the lateral 





